The invention relates to an apparatus for detecting a parameter at a plurality of slivers fed to a drafting system of a spinning machine, especially for detecting the movement and/or the presence of a sliver.
In a known form of apparatus, the parameter is measurable separately at each sliver, each sliver being drawn out of sliver cans over a respective driven supply roller and fed to the drafting system and being mechanically sensed by a feeler element, the deflections of which are convertible into electrical signals and which feeler element has a sensor element associated with it.
In the case of an apparatus described in WO 98/18985 A, guide rollers as well as eight measuring elements and eight cans for eight slivers are provided—looking upstream from a drafting system. Leads connect all measuring elements in parallel to a computer. The measuring elements each comprise a driven roller and a follower roll, which is mounted on a lever displaceable about an axis of rotation. The roller has a groove for the sliver, which groove can also be engaged by the roll for sensing the sliver. Each sliver entering the drawing system is sensed beforehand in a measuring element to detect a parameter. Possible parameters are preferably the weight, the thickness, the mass etc, in the form of absolute values or relative values, such as the changes in weight, thickness or mass. In this process, the roll is deflected by the volume occupied by the sliver on the roller, which is converted to an output signal proportional to this deflection. The output signals of all measuring elements are fed to the computer via the leads. Each measured value can be compared with a threshold value to ensure that a sliver is actually present, or that the sliver has reached a minimum volume. This dynamics of this mechanical feeling system of tongue and groove roller are not satisfactory at high delivery speeds. The feeler roller may be caused to oscillate owing to the large mass.
It is an aim of the invention to produce an apparatus of the kind described in the introduction that avoids or mitigates the said disadvantages, in particular is of simple structure and allows an improved and more accurate detection of the individual slivers.